Presently there are millions of shipping containers that enter and leave ports throughout the world. Under the current political and social climate, each container must be inspected to determine whether the container contains contraband such as narcotics, nerve or mustard gas, explosives, nuclear material and the like. Sensors that detect contraband are often placed within the container, thus requiring a communication means to communicate with a receiving or transmitting device that is external to the container.
Conventional shipping containers comprise thick metal walls that prevent electromagnetic signals from passing through the wall. Therefore, wireless communication between an internal sensor within the container and an external receiver/transmitter is very difficult. Solutions to the internal and external communication problem have included heat, x-ray, or wiring methods in which a hole is drilled in the wall of the container. These solutions are costly and undesirable.
Accordingly, a need exists for alternative sensors capable of wirelessly reporting a status to an exterior of an enclosure such as a shipping container.